How do you use a torque wrench?

Answer 1

Why Use a Torque Wrench?A bolt sitting on your workbench is at rest regardless of whether it is made of metal or rubber. When you install the bolt in an application and begin to tighten it with a wrench it begins to stretch and load up a force along its length. Just like a rubber bolt, if you tighten a metal bolt too much it will break the bolt (or damage the application), but if it's not tight enough it will not have the proper preload to hold the application together. You could just tighten up the bolt as much as you can, but in most cases an engineer has calculated how much "give" should be between the bolted surfaces to assure minimal wear and maximum application life in whatever bumpy, cyclic environment the bolt is designed to be used. The answer to achieving the proper amount of preload is to use a torque wrench, and just as importantly to use it correctly.

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You don't. If you want to do it right you need a torque wrench. It is more important than people think to torque fasteners properly.


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It is - you can do a lot of damage with incorrect or uneven tightening. If a proper torque-wrench is unavailable it is sometimes possible to use a strong spring-balance on the handle of a standard socket-set, and use the standard formula relating tension, length and torque, but that is potentially inaccurate it's far, far better to use the correct tool!

ALL of the above comments are absolutely correct- I would add only that just offhand I can think of 2 common applications on cars where use of a torque wrench is essential -Cylinder head bolts and trans pan bolts.

Answer 2

There are two basic kinds of torque wrenches - the "needle" kind and the "clicker" kind. The "needle" kind, which are wildly inaccurate and therefore pretty much worthless, have a needle which moves across a scale which supposedly shows the torque being applied. The "clicker" kind allow for the desired torque to be "dialed in" - usually by means of turning the base of the handle which moves to the desired torque setting on a scale in the handle; once set, the wrench will emit an audible "click" when a fastener (usually a nut) is tightened to the torque level at which it's set. When torquing wheel lug nuts, you should always work "crosswise" or in a star pattern rather than simply working your way around the lug nuts in a circle; this will ensure a closer torque setting. Once all lug nuts have been torqued this way, you should then work circularly around the nuts to double-check the torque setting. Wheel nut torque settings should be re-checked after each on-track session.